Yedikule Hisari (Seven Towers dungeons)
This seven towered fortress was built in the time of Sultan Fatih Mehmet to protect the treasury. In Murat III's reign, the treasury protected at Yedikule was relocated to the Topkapi Palace and Yedikule began to be used as a dungeon. The place of imprisonment of many foreign ambassadors and Ottoman statesman, as well as a place of execution for some, the fortress was last used as a prison in 1831. It than became a dwelling for the lions of Topkapi Palace, and later gunpowder manufacturing place. Today the fortress is a museum, also hosting open air concerts in its inner courtyard during the summer months.